Ground speed and drift indicator



Sept. 27, 1949. R. w. PHlLABAUM 2,482,795

v GROUND SPEED AND DRIFT INDICATR Filed May 27, 1946 2 Shets-Sheet l- ATTORNEY Sept. 27, 1949. R w, PHlLABAUM 2,482,795

GROUND SPEED AND DRIFT INDICATORv Filed may 27, 194e 2 sheets-sheet 2 g Z i' .//Wf/v/ae ATTODMEY Patented Sept. 27, 1949 UNITED.; STAT-ES TENT- OFFICE l f" *ff-'2,482,795

` -GRoUNDsPEE-DIAND DRIFT INDICATOR 1 L Robert YWayne 4Philabaum, deceased,-late of Elkhart County,Vl Ind., by Thelma Philabaum, administratrx, Elkhart, Ind. l. appliqatfnmaym, 1946, seria1No.672,499

- .comme (c1. .a3-46.5) l (Grant-ed ander thel act of March 3, 1883, as

The present invention concerns a combined ground speed and drift indicator for an aircraft.

v -An object of the invention is to providean inthe apparent speed of movement .of ground past Athe observers line of vision to afford an indication of the ground speed of the aircraft.

Further objects and advantages of this invention, as Well as its construction, arrangement and operation, are apparent from the following description and claims in connection with the accompanying drawings, in which, I g

Fig. 1 is a top plan view of apreferred embodiment of the invention. I

Fig. 2 is a front elevational viewof the embodiment shown in Fig. 1. .Y

Fig. 3 is a top plan View of the internal mechanism.

There is shown an instrument case .I I having a top I2, sides I3 and a motor case I4 depending therefrom. Instrument case `Il is mounted for `rotation upon an optical tube |5 having an of an observer. I

Mounted within case I3 upon vertical spindles I1 and I8 aretwo transparent dis-cs I9Y and 20 disposed in overlapping relation as shown.' at 2|. Discs I9 and 20are provided-with radial-indices 22 and 23 disposed in equally:spaced relation. Discs I9 and 20 are arranged for opposite vrotation.

Mounted on spindle |1 is a gear .24 drivenby a worm gear 25 mounted on a shaft 26 on the other end of which is mounted a spur gear 21. Mounted on spindle I8 is a gear 28 driven by a worm gear 29 mounted on a shaft 30 on the other end of which is mounted a spur gear 3|. f Spur gears 21 and 3| are driven by a pinion gear32 mounted on a shaft 33 on the other end of which is mounted a gear 34 driven by worm gear 35Ymounted on through a rheostat 40Vhaving a control knob 4| f and a switchv 42 to a suitable source of current l(not shown). Y g 1 :,1

When switch 42 is turned on, motor 31 rotates amended April 30, 1928; 370 O. G. 757) and causes opposite Vrotation of discs I9 and 2U with the result that indices 22 and 23 form a moving pattern in the overlapping portion 2| of the discs and such pattern moves in the direction of rotation of the discs. The speed of movement of this pattern is controlled by manual operation of knob 4| of rheostat 40, which directly controls the speed of rotation of motor 31.

Mounted on top I2 of case II above motor 31 is a tachometer 43 having a pointer 44 that moves in correlationwith the speed of rotation of motor 31. Tachometer 43 has a dial face 45 calibrated in terms of ground-speed units and at its periphery provided with an index 46. Mounted adjacent the periphery of dial face 45l is a scale 41 calibrated in terms of altitude units. Dial face l45 of tachometer 43 is mounted for rotation so .48 is provided for adjusting the angular position of dial face 45. n y

In top I2 of case I I above the overlapping portion 2| of discs I9 and 20 is an opening 49 through .which an observer sighting along optical axis I6 can view the moving pattern established by rotation of discs I9 and 20. A pair of parallel reference lines are provided on case II so that an observer looking through the instrument can vturnv case II upon tube I5 until reference `lines 50 are in alignment with the apparent direction of movement of the ground. n

vMounted on case II and concentric with the optical axis I6 oi"V the instrument is a scale 5| calibrated in angular degrees about opticaly axis l5 and provided with a zerol calibration 52 in alignment with a line .drawn midway between reference lines 50. Mounted upon optical tube I5 by means of screws 53 is a pointer 54. Pointer 54 is disposed so that a line drawn through optical axis I6 and pointer 54 is parallel to the longitudinal axis of the aircraft. When an observer turns case II -to bring reference lines v5|) into alignment with the apparent direction of movement of the ground, pointer 54 registers with scale 5| so as to indicate the angle of drift of reading is made with switch 42 in off position 3 so that motor 3l is not turning and so that discs i9 and 2li are stationary under Which condition case Il is rotated about optical tube l5 until reference lines 5U are brought into alignment With the apparent direction of movement oi the earth. The calibration at which pointer 54 registers withwscale 5l indicates the angle of drift of the aircraft.

After the drift observation is made, the ground speed of the vaircraft is determined with the case II in adjusted position; Adjustment knob 43 is turned to bring index mark A6 of tachometer dial face d5 into registration with the proper` calibration on scale 4i' corresponding with` the altitude at which the determination is to be 1 made. Conductors 38 andhig areuconnectedcto a suitable source of current n o town )r 'd switch i2 is thrown to the on position to start. rotation of motor 3l. This sin., turn causes Aop; posite rotation of discs le and 2S vvitii the result that the pattern formed by the over-lapping portion 2l of discs I9 and zdstartsgto move across the observers line of vision. Rlieosta't knob di is adjusted until the speed df the mving pattern is synchronized with theapparent speed of the irioverne'rit of the earth past the ooservers lineof vision. The calibration on dial '5 which is in registration with pointer ed of tachonieter 43 gives a reading of the ground speed of the aircraft. y l

It is to be understood that various modifications and changes 'can be made in this invention Without departing from the spirit and scope thereof as set forth in the appended claims.

The invention described herein may be manufactured and vi'sed by or for the Governmentcf the United States fof America for govermental purposes Without the payment of any royalties thereon 'rther'efonV Y What is claimed' is: i i M 1. A groun'dspeed indicator comprising a pair of oppo'sitely rotatable dis-cs", said discs having overl'appin'g transparent portions, indices on said `discs to form a moving pattern adapted to pass theline of vision oi bserv'erlooling t"o y tva'rd the groundineaiisv for vsyriclfirono'usly rotating said discs, means for controlling` the iotational speed of said discs to synchrorii'zem'oveine'n't of the pattern ii'rii'jln|` apparent movement xof theV ground past the 4oboeri/"ens line of vision, and

means responsive to rotational speed of said discs for lndicatinf'g gronndfspeed; i l

2,. A gremita-'speed iiiqi'aior comp'yisinga pair "ci transparent discs mounted mi fppsite'fsvnlchroni'zed rotation, "said discs'loeing mounted With portions thereof overl-'l p pmg, 4saiddi'scs 'having "a pluralityio'f equally-'spaced radial indices thereon, said indices upon rotation of vsaidjdi's'c's forming a rncivi'ngI pattern adapted to v'pas'is the'line of vision of anbServer looking toward the ground, an electric motor, Ta "geartrain interconnecting said motor and said discsiyvhereby rotation of said ,motor will cause opiisitej svneiinized io*- tationA o'fjsaid discs', a rheostat connected -with saidinotor `vvh'eeloy adjustment of- 'the rheostat controls the motor 'speedand speed of rotation of said discsfsow'that said moving pattern :can be synchronized with apparent invernent oi `th'e :gemid pesi 'uit' Qsrr'fs ,.llineof. 'Visioni la. tachometerconnected With said motor and vhaving avpcinter responsive bto rotational 'speed vof /s'aid motor, said tachoneter'having dial facfe calibrated i n units of ground yspeedY a'ii'd having `'indexenl thei'eripfhery ftliereof, 'a iiiid ale located at the periphery of l'said dial f'ae'and di calibrated in units of altitude, said dial face being mounted for rotation so that said index can be brought into registration with said fixed scale. 3'. A ground-speed indicator comprising a pair of transparent discs mounted for opposite syn chronized rotation, said discs being mounted With portions thereof overlapping, said discs having a plurality of equally-spaced radial indices thereon, said indices upon rotation of said discs forming a moving pattern adapted Ato pass the line of vision of van dbserve looking toward the grotind, a motor, means connecting said motor and discs vvhereby operation of said motor causes Opposite synchronized rotation of said discs, means for Y"controlling the rotational speed of said discs so tliattheV moving pattern can be synchronized with apparen movement of the ground past the observersiline of, vision, a tachometer responsive to rotational speed of said discs, said tachometer having a dial face with caiibrations and having an indexA on the periphery thereof, a iixed scale located at the periphery of said dial face, said dial -face being mounted for rotation so that said index can be brought into registration With said fixed scale.

4. A groun'dlspe'ed indicator comprising a pair of transparent discs .mounted for oppositesyll.- chronized rotation; said discs being mountedwith portions thereof overlapping; saidfdiscs having a plurality of equally-spacedradial indices thereon, said indices upon rotation vof said discs forming a moving pattern adapted topass the line of vision of an observer looking toward the ground, a motor, means connecting said motor and discs whereby operation of saidmotor :causes opposite synchronized rotation ofsaid discs, means for controllingthe rotational speed of said discs s0 that the moving pattern can be synchronized With apparent movement of the ground Dastthe observers line of vision, a tachometer responsivefto rotational speedV ofrsaid discs, and means l for compensating saidl tachometer in correlation with the altitude at Which anpbservatijon is made.

5. An indicating instrument comprisin'gasupport member, a casing -member mounted for rotation aboutan'axis on :said support member, said axis establishing a line of Vision of an observer, indicating Ameans associatedwith said membersfor indicating the nangular :position of Vrotation ofsaid casing memberL relative to said support member to indicate driftangle, a pair of oppositely rotating ydiscs, on Said casing member, said discs having overlappingA transparent portions', indices onsaid discs to form a moving pattern adapted to pass 4the observers line of vision, means for synchronously rotating said discs, means foricontrolling the rotational speed of said means to 'synchronize movement of the pattern with apparent movement of the ground past the observers line of vision, and means responsive 'to rotational 'spee'd of said-discs for indicating ground speed.' i

'6.` An indicating instrument comprising a pair of transparent :discsmurited vfoi` 'opposite synchronized rotationysaid discs being mounted with portions thereof overlapping, s'ai'd Ydiscs having Ya plurality of edually-'sp'aded radial indices thereon,

said indices upo'n rotation of said discs forming controlling the rotationa1 speed of fsaid'fd'isc's Yso that the moving #pattern canA .be L's'ynch'rcnized THELMA PHILABAUM, .l m

Administratria: of the Estate ofrRobert Wayne Philabaum, Deceased.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,919,126 Perkins July 18, 1933 2,413,683

Caldwell Jan. 7, 1947 

